In U.S. Pat. No. 3,589,167, which issued June 29, 1971 to the assignee of the present invention, there is disclosed a thermomechanical analysis apparatus. That apparatus includes a probe assembly which is suspended in substantially weightless contact with a sample material over a range of displacement of the probe. This substantially weightless contact is achieved by means of a fluid reservoir and a float which is submerged in the fluid and coupled to the probe. Weights are added manually to the probe assembly to just offset the buoyancy of the float. As the height of a sample under test changes, the substantially weightless probe moves up or down in response.
Vertical movement of the probe assembly of the referenced prior art device is sensed by a conventional linear variable differential transformer (LVDT). The magnetic core of the LVDT is mounted on a non-magnetic rod which supports the probe. In this prior art device, a rack and pinion are provided for moving the LVDT coil assembly to achieve a null prior to beginning a measurement. The rod member which supports the probe passes through a pair of roller bearings. The entire assembly is suspended from a frame at a pair of spaced support points.
It is an object of the present invention to provide an apparatus which is simpler to use and more accurate than that of the prior art. Another object is to provide such an apparatus which eliminates the need for a fluid and a float. Another object is to provide such an apparatus wherein the use of weights during analysis is not required. Another object is to provide such an apparatus wherein mechanical adjustment of the LVDT for nulling purposes is avoided. Another object is to provide such an apparatus wherein friction is reduced by omitting bearings. Another object is to provide such an apparatus wherein potential friction and misalignment problems arising from a two point support are eliminated. The manner in which the foregoing objects are achieved will be more apparent from the following description and appended claims.